DE840391C - Process for the production of a gas mixture suitable for urea synthesis from ammonia water - Google Patents

Description

Process for producing a gas mixture suitable for urea synthesis from ammonia water The production of an ammonia-carbon dioxide mixture suitable for urea synthesis with the composition 2 mol NH3 to 1 mol C02 from the ammonia water obtained during the dry distillation of bituminous fuels is difficult because it is raw or compressed, contains too little carbon dioxide (generally only 0.5 to 0.7 moles per 2 moles of NH 3), but larger amounts of hydrogen sulfide (about 0.1 to 0.1 moles per 2 moles of NH 3). So the missing carbon dioxide has to be replenished and the hydrogen sulphide, which interferes with urea synthesis, has to be removed.

The latter can be done by deacidifying the diluted or compressed ammonia water at overpressure or atmospheric pressure, but if the desulfurization of the water is to be complete, especially in the deacidification of the "dilute ammonia water, considerable amounts of carbon dioxide are always transferred into the deacidification fumes, so that, for. For example, if the pressure deacidification is carried out below 10 atmospheres, the ammonia water only contains 0.1 to 0.2 moles of CO 2 or even less to 2 moles of NH 3 will.

To avoid it, one could think about deacidifying the To do without ammonia water and instead use the ammonia water sulfur-binding Means, e.g. B. iron oxide hydrate masses to treat, but this process is with associated with various inconveniences and especially for the synthesis of urea therefore not very suitable, because the missing C02 is added somewhere here must and it is therefore advantageous as in the present method for deacidifying of the water can draw.

It has been found that the ammonia water is advantageously treated in such a way that it is deacidified, optionally with the introduction of additional carbon dioxide, and the deacidification vapor consisting essentially of CO and H, S is desulphurized dry using a suitable gas cleaning compound. The practically pure carbon dioxide that remains behind is returned to the system so that any loss of CO 2 is avoided. The removal of the hydrogen sulfide takes place, as it were, in two stages; in the first, deacidification, only the H2 S is separated from the NH .; and a part of the CO, instead of, in the second the CO 2 is separated from the H, S with the conversion of the latter into a solid form (iron sulphide or sulfur).

For desulfurization of the deacid vapor one can use an alkalized iron oxide hydrate mass as a gas cleaning mass with advantage and at atmospheric or elevated pressure, z. B. that of the deacidifier, work. The carbon dioxide, which was introduced into the deacidifying column or also driven off to facilitate and complete the removal of hydrogen sulfide, is obtained in pure form. This is compressed either on its own or together with the carbon dioxide still missing in the ratio 2 N H3: 1 CO, then compressed together with the ammonia-carbon dioxide mixture obtained from the deacidified water by pressure removal and fed to the autoclave used for the urea vapor. However, the amino-carbon dioxide mixture leaving the deacidifier and the desulphurized carbon dioxide can also be brought to the pressure required for the synthesis, each of which is an advantage.

The ammonia-carbon dioxide mixture, which is driven off from the Deacidified water is obtained, should contain less than io °; 'o water, so A good uranium yield is guaranteed during the synthesis. For this it is necessary the output of the ammonia-carbon dioxide mixture from the deacidified water to carry out a higher pressure than that used for deacidification.

The following is a numerical example of the method for diluted and explained in more detail for compressed ammonia water. Example iooo parts diluted Ammonia water, which contains 10 parts of ammonia, 9 parts of carbon dioxide and 2.5 parts of hydrogen sulfide contains, are deacidified at io atü on a colony, whereby a plume is obtained which contains 5 parts of carbon dioxide and 2.5 parts of hydrogen sulfide, while with the deacidified water, 10 parts of ammonia and 4 parts of carbon dioxide are drained off. The deacidification vapor is placed in pressure-resistant towers filled with iron oxide hydrate mass freed from hydrogen sulfide, with the parts used in pure carbon dioxide Shape to be regained.

The deacidified water is either initially converted into strong ammonia water compressed or immediately, without prior cooling, one working at 20 atmospheres Abort supplied, which is held in its upper part at about 12o °, so that with the withdrawing 10 parts of ammonia and 4 parts of carbon dioxide only 1 part of water escapes. The 5 parts leaving the dry desulphurisation become carbon dioxide mixed with a further 4 parts of carbon dioxide, precompressed to 2o atm and the at Output obtained ammonia-carbon dioxide Gemiscli supplied, whereupon in the compressor the entire synthesis gas mixture to that required for urea synthesis Pressure of about 15o atm. is further compressed and fed to the autoclave. In the autoclave 5.3 parts of urea are formed and 7 parts of ammonia and 9 parts when the air is blown off Get back carbon dioxide, which go back as cycle gas and together with further carbon dioxide is initially pre-compressed to 2o atm and then together with new one Amnionia-carbon dioxide mixture in the compressor to the level required for urea synthesis Pressure to be brought.

Of course, both the carbon dioxide and the cycle gas mixture can be used be compressed more highly and at a suitable point in the newly introduced Ammonia-carbon dioxide mixture are introduced. Example 2 10000 parts compacted Ammonia water containing 17o parts ammonia, 16o parts carbon dioxide and 30 parts Hydrogen sulfide, without the application of pressure, with the addition of 60 parts Carbon dioxide, deacidified on a column. The deacid vapor that escapes in the process contains 3o parts hydrogen sulfide and 50 parts carbon dioxide, which deacidified the runoff Ammonia water Uo parts ammonia and 17o parts carbon dioxide. The deacidification steam is removed from hydrogen sulphide in cleaning boxes filled with iron oxide hydrate mass freed.

The deacidified water becomes one at 20 atm without prior cooling. working abortionist, which is kept in its upper part at iio to 13o °, fed. From this one draws from 17o parts ammonia and 17o parts carbon dioxide existing gas mixture, which also contains 28 parts of water.

The carbon dioxide (50 parts) leaving the detergent boxes is on 2o atm. compresses and arrives together with the gas mixture generated during the downforce in the compressor, in which the entire mixture is used for urea synthesis required pressure is brought. The treatment of the cycle gas mixture happens as indicated in the first example.

Claims (1)

j> ATE \ TAISPRL "CH: Process for producing one for urea synthesis suitable gas mixture of ammonia water (gas water), characterized in that that the diluted or compressed ammonia water, optionally using by pressure and / or with the addition of carbon dioxide, initially deacidified, the deacidification vapor dry desulphurized with gas cleaning mass and the desulphurized ammonia water drives off under such a pressure that the ammonia-carbon dioxide mixture which is withdrawn contains less than zo per cent of water, as is the case with dry desulphurisation recovered carbon dioxide, optionally with the addition of further carbon dioxide compressed with the ammonia-carbon dioxide mixture or separately from it.